Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sandia/UNM self-assembly process forms durable nanocrystal arrays and independent nanocrystals

27.04.2004


NOW, SIT UP: Jeff Brinker (left) and Hongyou Fan observe satisfactory fluorescence by their well-trained nanocrystals in water solution. The dark vial holds gold nanocrystals; the orange and green are semiconductor nanocrystals. (Photo by Randy Montoya)


Top image: ordered gold nanocrystal packed inside silica. Electron diffraction pattern (left corner image) and high-resolution image (right corner) confirmed the nanostructure and gold nanocrystals. Bottom image: self-assembled, well-shaped gold nanocrystal/silica arrays.


Possible uses include biological labeling, laser light, catalysts, memory storage, and relief for physicists

A wish list for nanotechnologists might consist of a simple, inexpensive means - actually, any means at all - of self-assembling nanocrystals into robust orderly arrangements, like soup cans on a shelf or bricks in a wall, each separated from the next by an insulating layer of silicon dioxide.

The silica casing could be linked to compatible semiconductor devices. The trapped nanocrystals might function as a laser, their frequency dependent on their size, or as a very fine catalyst with unusually large surface area, or perhaps a memory device tunable by particle size and composition.



Or perhaps the technologist might want to stop nanocrystals from clumping. Agglomeration prevents them from being used as light-emitting tagging mechanisms to track cancer cells in the body and from being used in light-emitting devices needed for solid state lighting.

In this week’s journal Science, researchers at the National Nuclear Security Administration’s Sandia National Laboratories and the University of New Mexico describe a simple, commercially feasible method for doing both these things.

"The paper overcomes barriers to using nanocrystals routinely," said Jeff Brinker, Sandia Fellow and UNM chemical engineering professor, who with Sandia’s Hongyou Fan led the self-assembling effort. "The question in nanotechnology isn’t ’where’s the beef,’ it’s ’where’s the connectors’? How does one make connections from the macroscale to the nanoscale? This question lies at the heart of nanotechnology."

The self-assembly approach developed by the SNL/UNM teams allows nanocrystal arrays to be integrated into devices using standard microelectronic processing techniques, bridging huge gaps in scale.

Said IBM staff researcher Chuck Black at T. J. Watson Research Center in Yorktown Heights, NY, "One thing that’s nice is that these materials are hard materials. Often they come with an organic surfactant layer that makes it difficult to process materials, like a kind of grease. This material is embedded in oxide. It sounds like a neat thing and a new approach." The Sandia/UNM approach scrubs the surfactants with an ozone compound.

"Also, quantum dots can be important for biolabeling and biosensing," said Fan, who initiated the effort to use the nanocrystals for those purposes. "The beauty of our approach is that it makes these quantum dots both water-soluble and biocompatible, two essential qualities if we want to use them for in vivo imaging. The functional organic groups on the quantum dots can link with a variety of peptides, proteins, DNA, antibodies, etc. so that the dots can bind to and help locate targets like cancer cells, a critical issue in biomedicine."

Sandia has applied for a patent on this approach, which should aid attempts at several major universities to identify individual cancer cells before they increase in number.

(Researchers have found that at the nanoscopic realm, changing merely the size of a material changes the frequency it emits when ’pumped’ by outside energy; thus, quantum dots of particular sizes and material will emit at predictable frequencies, which makes them useful adjuncts when bound to molecules created to bind to particular cancer molecules.)

The process uses a simple surfactant (similar to dishwashing soap) to surround the nanocrystals - in this case, made of gold - to make them water soluble. Further processing involving silica causes the gold nanocrystals to arrange themselves within a silica matrix in a lattice - a kind of artificial solid with properties that can be adjusted through control of nanocrystal composition, diameter, properties of the surfactant, and/or stabilizing ligands used in formation of the water soluble nanocrystals.

The robust 3-D solids, which are stable indefinitely, demonstrate the incorporation of nanocrystalline arrays into device architectures.

A further use allows physicists to go beyond modeling to determine how current scales with voltage in nanodevices. "Before," says Brinker, "there was no way to make precisely ordered 3-D nanocrystalline solids, integrate them in devices, and characterize their behavior. There was no theoretical model. How does the current decide which way to hop between crystals?"

The new material can be used as an artificial solid to test out theories. "It should be a dream for physicists; they don’t just have to model anymore," said Brinker.

A kind of choreographed transmission possibility exists with the so-called "coulomb blockade," he said: No current is passed at low voltages because each crystal is separated by a thin (several nanometer thick) layer of silica dioxide, creating an insulator between the stored charges. Each nanocrystal charges separately. "This could be configured into a flash memory," said Brinker, "with a huge number of charges stored in an array of nodes."

Researchers at UNM’s Center for High Technology Materials performed experiments to establish the current/voltage scaling characteristics of the gold/silica arrays as a function of temperature. Sandia researcher Tim Boyle made and provided nanocrystal semiconductor (cadmium selinide) quantum dots.

Neal Singer | Sandia!
Further information:
http://www.sandia.gov/news-center/news-releases/2004/micro-nano/nanotoolcase.html

More articles from Process Engineering:

nachricht Gluing with the Laser
30.06.2015 | Laser Zentrum Hannover e.V.

nachricht Innovative Modular Process Makes Plastic Film Coating Highly Efficient
09.06.2015 | Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: X-rays and electrons join forces to map catalytic reactions in real-time

New technique combines electron microscopy and synchrotron X-rays to track chemical reactions under real operating conditions

A new technique pioneered at the U.S. Department of Energy's Brookhaven National Laboratory reveals atomic-scale changes during catalytic reactions in real...

Im Focus: Iron: A biological element?

Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and a half billion years ago.

Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and...

Im Focus: Thousands of Droplets for Diagnostics

Researchers develop new method enabling DNA molecules to be counted in just 30 minutes

A team of scientists including PhD student Friedrich Schuler from the Laboratory of MEMS Applications at the Department of Microsystems Engineering (IMTEK) of...

Im Focus: Bionic eye clinical trial results show long-term safety, efficacy vision-restoring implant

Patients using Argus II experienced significant improvement in visual function and quality of life

The three-year clinical trial results of the retinal implant popularly known as the "bionic eye," have proven the long-term efficacy, safety and reliability of...

Im Focus: Lasers for Fast Internet in Space – Space Technology from Aachen

On June 23, the second Sentinel mission was launched from the space mission launch center in Kourou. A critical component of Aachen is on board. Researchers at the Fraunhofer Institute for Laser Technology ILT and Tesat-Spacecom have jointly developed the know-how for space-qualified laser components. For the Sentinel mission the diode laser pump module of the Laser Communication Terminal LCT was planned and constructed in Aachen in cooperation with the manufacturer of the LCT, Tesat-Spacecom, and the Ferdinand Braun Institute.

After eight years of preparation, in the early morning of June 23 the time had come: in Kourou in French Guiana, the European Space Agency launched the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Conference on Regenerative Medicine in Leipzig: Last chance to submit abstracts until 2 July

25.06.2015 | Event News

World Conference on Regenerative Medicine: Abstract Submission has been extended to 24 June

16.06.2015 | Event News

MUSE hosting Europe’s largest science communication conference

11.06.2015 | Event News

 
Latest News

Offshore wind park Westermost Rough officially inaugurated

01.07.2015 | Press release

Siemens Velaro train wins "Red Dot" award

01.07.2015 | Awards Funding

Liquids on Fibers - Slipping or Flowing?

01.07.2015 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>